Only one of the guys in the photo can stand for the Australian parliament. Photo: Martin Hunter/Getty Images

New Zealand’s internal affairs minister, Peter Dunne, has confirmed Australian deputy prime minister Barnaby Joyce is a New Zealand citizen under his country’s 1948 Citizenship Act.

Dunne told the media in New Zealand that Crown Law had checked the circumstances and confirmed Joyce was a citizen.

The announcement will put pressure on the Nationals leader to step aside from the Cabinet, like former minister Matt Canavan, who resigned from the Turnbull ministry last month over concerns that he may be a dual Australian-Italian citizen, in breach of the Australian constitution. The High Court is due to hear the Canavan matter on August 24.

Australian-born Joyce, whose father is New Zealand-born, is referring his eligibility to sit in parliament to to the High Court.

Announcing he could potentially be a Kiwi by descent in parliament this morning, Joyce said he was staying on as a minister and deputy PM at prime minister Malcolm Turnbull’s request based on “the strength of the legal advice the Government has received” from the solicitor-general, which “is of the firm view that I would not be found to be disqualified”.

In parliament today, Labor citizenship spokesperson Tony Burke said that the High Court was making history because it was effectively ruling whether the government could continue with a majority of one and that Joyce should step aside as a minister and deputy leader.

“If the Minister for Resources was able to stand aside even though he had the Attorney General beside him claiming that he had a strong case then why on earth is strong case the defense for the Deputy Prime Minister? How on earth does that work? It cannot be the case that the words of the Attorney General in defending Senator Canavan and why he wouldn’t resign from Parliament were correct, because they apparently had a strong case, yet stood aside,” Burke said.

“But if it’s the Deputy Prime Minister, the person who’s the architect of the Coalition agreement with the Prime Minister on which the fate of this Government hangs that secret deal, then in that situation, the rules all change.

“This is a Deputy Prime Minister who himself opened Parliament today saying that he’s not sure whether he’s validly elected. That’s why it’s being referred to the High Court. You don’t refer something to the High Court because you think there’s no doubt; you refer something to the High Court because you just don’t know. And if you just don’t know, you should not be Deputy Prime Minister of Australia right now. If you just don’t know, we should not be relying on your vote, and we should not have a situation where penalty rates were cut off the back of your vote, where we don’t have a banking royal commission on the back of your vote.”

Joyce joins four Australian politicians – two Greens, who resigned and two hoping to hold onto their current jobs – awaiting the court’s decision.

Queensland One Nation senator Malcolm Roberts, who was a British citizen, is also heading to the High Court, along with former Turnbull government minister Matt Canavan, who stepped down from Cabinet after discovering that his mother registered the 36-year-old Australian-born Queensland senator as an Italian citizen a decade ago, but did not tell him.

Two Greens senators resigned from parliament last month after discovering they were dual citizens because of their birthplace.

Section 44 of the Constitution bars people with citizenship in a country other than Australia from standing for election.

Prime minister Malcolm Turnbull wrote to opposition leader Bill Shorten today asking if he wanted to refer any Labor MPs to the High Court too “in the national interest”.

Shorten has previously said that the party is confidence there are no doubts over any of its MPs.